Electronic system for the stimulation of biological systems

ABSTRACT

A receiver totally implanted within a living body is inductively coupled by two associated receiving coils to a physically unattached external transmitter which transmits two signals of different frequencies to the receiver via two associated transmitting coils. One of the signals from the transmitter provides the implanted receiver with precise control or stimulating signals which are demodulated and processed in a signal processor network in the receiver and then used by the body for stimulation of a nerve, for example, while the other signal provides the receiver with a continuous wave power signal which is rectified in the receiver to provide a source of electrical operating power for the receiver circuitry without need for an implanted battery.

United Sta tes Patent 1191 Lenzkes Apr. 17, 1973 [5 ELECTRONIC SYSTEMFOR THE 3,662,758 5/1972 Glover "128/419 12 STIMULATION OF BIOLOGICALSYSTEMS Primary Examiner-William E. Kamm At: -Ed dB.J hn [75] Inventor:Herbert H. Lenzkes, Pomona, Calif. omey war 0 son [73] Assignee: GeneralDynamics Corporation, Po- ABSTRACT mona Cahf- A receiver totallyimplanted within a living body is in- [22] Filed; June 5 7 ductivelycoupled by two associated receiving coils to a physically unattachedexternal transmitter which PP 153,316 transmits two signals of differentfrequencies to the receiver via two associated transmitting coils. Oneof 1 52 us. 01. ..128/422 128/419 E the Signals the transmitter Providesthe [51} Int Cl A61 1/36 planted receiver with precise control orstimulating [58] Fieid 0. 419E Signals which are demodulated andprocessed ina 128/419 P 422 2 1 signal processor network in the receiverand then used by the body for stimulation of anerve, for example, whilethe other signal provides the receiver with a continuous wave powersignal which is rectified in the [56] References Cited receiver toprovide a source of electrical operating UNITED STATES PATENTS power forthe receiver circuitry without need for an implanted battery. 3,236,2402/1966 Bradley ..l28/4l9 E 3,195,540 7/1965 Waller ....l28/419 P 9Claims, 13 Drawing Figures 3,646,940 3/1972 Timm et al ..l28/4l9 EELECTRONIC SYSTEM FOR THE STIMULATION OF BIOLOGICAL SYSTEMS BACKGROUNDOF THE INVENTION tremities, controlling spasticity, stimulatingparalyzed l0 urinary bladders and preventing atrophy in clinicalapplications and for functional and behavioral changes inneurophysiological applications, for example. The system of theinvention utilizes a pulse position modulation technique forelectricallystimulating biological systems such as nerves, for example,in a manner which presently does not exist. The resulting stimulationoutput is a constant current biphasic or monophasic signal. Because ofthe digital nature of the inventive system, accurate and reliablecurrent stimulating levels are achieved with fast rise and fall times.Safety features have been included in the system to prevent extraneousstimulation due to interfering signals. When the implanted receiver isnot activated by the external transmitter, any extraneous signals areshunted by a low impedance path in the receiver.

The inventive system is essentially digital in nature, whereas knownsystems in the prior art employ analog techniques. In addition, theprior art systems employ pulse width modulation in which the resultingpulsed radio frequency signal is detected and filtered to obtain astimulation waveform. This prior art method, while simple in nature, hasmany limitations. For example, it cannot provide a precisely controlledamplitude because of its dependency on the coupling coefficient betweena primary tuned circuit and a secondary tuned circuit, it cannot providea biphasic stimulation waveform nor can it generate a direct currentstimulation. In addition, its unipolar pulses are not rectangularbecause an exponential discharge circuit is normally employed.Stimulators of the prior art are designed for specific applicationsandlack the parameter versatility and safety that can be achieved withthe inventive system.

SUMMARY OF THE-INVENTION The system of the present invention includes atransmitter that is inductively coupled by two transmitting coils to areceiver located totally within a living body. The system of the presentinvention is sometimes called a Biostimu]ator" and at other times aTelestimulator The transmitter, which is located outside the body,transmits two signals of different frequencies to the receiver via thetwo transmitting coils. The dual frequency link of the system providesthe implanted receiver with control signals or operating information andalso a signal from which the receiver can extract its electricaloperating power. The receiver basically comprises two receiving coils, asignal processor and a power supply. The output of the receiver iscoupled to two electrodes via very small electrical wires which may beattached to a nerve, for example, to stimulate the nerve or to block it.The desired stimulating pulse characteristics such as amplitudes, width,interpulse, periods, etc., are initially entered into the control panelof the transmitter via suitable switches such as rotary thumbwheelswitches, for example. These data are converted to a digital format partof which is transmitted to the receiver as a 21-bit Amplitude Data Word.This information is received, decoded and stored by the signal processorportion of the receiver to provide the proper amplitude reference tostimulate the nerve. The remaining portion of the data which has beenpreviously entered into the transmitter is sent to the receiver as aseries of Stimulation Words. Each of the Stimulation Words comprisesthree 5-microsecond radio frequency (r-f) pulses at substantially 27.12MHz. The time spacing between the pulses determines the time duration ofthe various parts of the stimulating waveform. Each word operates inreal-time to alternately stimulate the nerve with a positive amplitude,a negative amplitude and a zero amplitude. The transmitter also providesa substantially KI-Iz continu ous wave power signal which is inductivelycoupled into the power supply coil in the receiver and rectified toprovide electrical power for the receiver circuitry.

The power signal is always present whenever the sytem is in use.

Therefore, it is an object of this invention to provide an electronicsystem for the stimulation of biological systems in a living body in theform of an implantable receiver capable of providing proper stimulationwhen used in conjunction with an external transmitter.

Another object of this invention. is to provide an electronic system forthe stimulation of biological systems in a living body in which nointernal batteries are utilized nor any direct wire connections into thebody are made.

It is a further object of this invention to provide a stimulator systemfor a living body wherein a dual .frequency external transmitterprovides inductively coupled control and power signals to a compatiblereceiver located within the living body.

Other objects and features of the invention, as well as the manyadvantages thereof, will be readily apparent to those skilled in the artfrom a consideration of the following written description andaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1' is a simplified functional.block diagram illustrating the overall system involved in the presentinvention.

FIG. 2 is a dimensioned view of an encapsulated embodiment of theimplantable receiver of the system.

FIG. 3 is a diagrammatic showing of the receiver of FIG. 2 implanted inan arm and an embodiment of an associated transmitter.

FIG. 4 is a functional block diagram of the transmitter shownin FIG. 3.

FIGS. 5a-5h show electrical waveforms available from the transmitter asstimulation words and the resulting stimulating currents.

FIG. 6 is a functional block diagram of the receiver shown in FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT diagram of the overall systemwhich includes a transmitter 10, which may be of the laboratory type,for example, externally located with respect to the outer surface of askin portion 12 of a living body (not shown). Stimulating and.operational information data for operation of the transmitter are listedin FIG. 1. A 100 KHZ analog channel network 14 in transmitter 10provides a substantially 100 KHz continuous wave power signal to acapacitor 16 and a coil or inductor 18 which comprise a substantially100 KHz series resonant circuit 20. The coil 18 acts as a transmittingantenna. A 27.12 MHz analog channel network 22 in transmitter 10provides pulsed radio frequency data at substantially 27.12 MHz to acapacitor 24 and a coil or inductor 26 which comprise a substantially27.12 MHz parallel resonant circuit 28. The coil 26 acts as atransmitting antenna. Coupled to the 100 KHZ analog channel network 14and to the 27.12 MHz analog channel network 22 by connecting leads A, Band C is a transmitter logic network 29 which processes the stimulatingand operational information data listed in FIG. 1.

In practice, the capacitor 16 in the resonant circuit 20 (beingrelatively large in size) is physically located with the othercomponents of the 100 KHz analog channel network 14, whereas theinductor 18 of the resonant circuit 28 together with the inductor 26 andcapacitor 24 of the resonant circuit 28 are encased in a suitableprotective housing and as a unit, the combination is sometimes calledthe transmitter probe. Each of the circuits encased in the probe ispreferably connected to its respective channel by a coaxial cable (notshown).

As a point of interest, the simple resonant circuit 28 could be changed,if desired, to a preloaded, tapped resonant circuit wherein a resistoris connected in parallel with the inductor 26 and two series capacitorsare connected in parallel with the resistor/inductor combination. Thecenter conductor of the appropriate coaxial cable would be connectedbetween the two series capacitors.

The particular frequencies chosen for the preferred embodiment are byway of example only, and it is well understood by those skilled in theart that other frequency combinations as authorized by FCC regulationsmay be substituted.

Positioned completely underneath the skin portion 12 is'an implantablereceiver 30 which includes a coil or inductor 32 connected in parallelwith a capacitor 34 which comprise a 100 KHz parallel resonant circuit36. The inductor 32 acts as a receiving antenna to receive theinductively coupled 100 KHZ power signal from the inductor 18 of theresonant circuit 20. The received power signal is rectified andregulated in a power supply circuit 38 to provide electrical power ofthe proper potential for the implanted electronics via conductors 40, 42and the reference ground 41. A coil or inductor 44 is connected inparallel with a capacitor 46 and comprise a 27.12 MHz parallel resonantcircuit 48. The coil 44 acts as a receiving antenna to receive theinductively coupled 27.12 MHz control or operating information signalfrom the coil 26 of the resonant circuit 28. The received control signalis processed in a signal processor network 50 the output of which isconnected via male interconnect conductors 52, 54 and very small wiresto a nerve 56, for example. In describing the preferred embodiment ofthe present invention, nerve stimulation has been chosen as one exampleonly of the many uses thereof, and it will be readily understood bythose skilled in the art that the present invention can be used in manyclinical and neurophysiological applications.

Utilization of microelectronic fabrication techniques during the pastfew years has resulted in an electronic packaging science wherein manycomplex electronic circuits can be condensed into small packages. As anillustration of the science of microminiaturization, FIG. 2 shows thedimensions of an actual size example of the receiver 30 of the presentinvention contained in a 0.25

inch thick circular package of 1.25 irich diameter. This small sizeallows utilization of the receiver 30 in most parts of the human body.In the example of FIG. 2, the implantable receiver 30 is contained in ahermetically sealed allceramic package which is encapsulated withmedical-grade silicone rubber 58, for example, to reduce the possibilityof body contamination and rejection. The majority of the electroniccircuitry is contained on two circular ceramic substrates (not shown).This circuitry generally consists of thick film resistors, chipcapacitors, and various semiconductor chips and interconnections. Thepower supply coil 32 of the receiver 30 is concentrically wound on theouter edge area of a ceramic circular coil form (not shown) which alsoserves as a housing for the two circular substrates. The signal coil 44is printed on the outside portion of one of the circular substrateswhich also acts as a cover for one end of the unit. The maleinterconnectors 52, 54 are imbedded in the power supply coil form toprovide mechanical integrity. The all-ceramic package is extremelyrugged and will survive in very adverse environments. The implantablereceive 30 is surgically placed within a desired body area as shown inFIG. 3 and is preferably affixed to the nearest bone structure. In FIG.3, the receiver 30 is affixed to the humerus 60 of an arm 62 by usingsynthetic materials similar to those used for bone repair, for example,and the receiver output interconnectors 52, 54 are connected to a nerve64 via very small electrical wires (not shown). In practice, the freeends of two electrical conductors (not shown) having female connectorson the other ends are attached to the nerve to be stimulated.

The female connectors are then slipped over the male interconnectors 52and 54. Also shown in FIG. 3 'is an example of the transmitter 10 withits output cabling 66, preferably two coaxial cables, and the encasedtransmitter probe in a housing 68. The transmitter coils 18, 26 in theprobe" housing 68 are wound similarly to receiving coils 32, 44 on acircular coil form or on individual coil forms and are protectivelyencased or encapsulated in a strong plastic material, for example.Stimulation of the nerve 64 is achieved by placing the transmitter coils18, 26 contained in the housing 68 approximately, for example, one-halfinch near, or actually on, the skin portion closest to the implantedreceiver 30 so the receiver coils 32, 44 can easily receive thetransmitted signals and then activate the transmitter. The operatinginstructions listed in FIG. 1 are entered into the transmitter 10 priorto stimulation via suitable switches as shown in FIG. 3 in which actualvalues are depicted to illustrate an exemplary operational setup. Alsoshown in the FIG. 3 example of a transmitter are the switches listed inFIG. 1.

Two major problems must be considered in the design and fabrication ofdevices to be implanted in a living body. These two major problemsinvolve the selection of enclosure and connector materials. The bodyfluids present a rather formidable challenge to the enclosure or coverfor an implantable device because of their corrosive action. Materialsthat provide longterm protection to the devices electronics and that arecompatible with the body chemistry are: ceramic, glass, syntheticresinous materials and some metals such as surgical-grade stainlesssteel and platinum, for example. The qualitiesthat make anall-ceramic-package a highly desirable choice for implantabledevicesinclude: mechanical strength, electrical isolation, resistance to bodyfluids, adequate thermal conductivity, compatibility with hybridtechnology and low cost. All connectors must be small and reliable andmust also be compatible with the body fluids. The conductors used forthe nerve stimulator described herein are made of stainless steel butcould also be made of platinum, gold, silver and tantalum or alloys ofthese metals, for example. Encapsulating materials should beelectrically insulating, inert, non-toxic, non-irritating andsterilizable. In addition to the silicone rubber 58, other examples ofencapsulant materials are: silastic resins, vinyl chloride, acrylicpolymers, polystyrene, tetrafluoroethylene polymers and the like.

Referring now to FIG. 4 there is shown a functional block diagram of thetransmitter 10., The stimulating word(s) and operational informationdata shown in FIG. 1 are again included in FIG. 4. The analog portion ofthe transmitter consists of two channels, one at 100 KHZ and the otherat 27.12 MHZ, which are functionally identical. The 27.12 MHz analogchannel network 22 comprises an oscillator 70 connected through a seriesswitch 72 to a power amplifier 74. The 100 KHzanalog channel network 14comprises an oscillator 76 connected through a series switch 78 to apower amplifier 80. The connecting leads A, B and C to the transmitterlogic network 29 are shown. Lead A is connected to the output of the 100KHZ oscillator 76, load B is connected to an input of the 100 KHz seriesswitch 78 and lead C connects to an input of the 27.12 series switch 72.Each of the power amplifiers 74, 80 is preferably connected to itsrespective resonant circuit 28, 28 via a coaxial cable as discussedhereinabove. In each channel, the series switch gates the signal fromthe appropriate oscillator to the amplifier as a function of thecontrolling logic. The 100 KHz oscillator 76 is also used to develop allof the timing functions required by the digital portion of the receiver30 to be described hereinafter.

Connected to the 100 KHZ series switch 78 is anoutput of a program logiccircuit 84 in the transmitter logic network 29 to which is coupled afull decoder network 88. A time duration counter circuit 86. isconnected to the counter full decoder network 88. Another output of theprogram logic circuit 84 is connected to a data register 90, a datadecoder 92 and a mode logic circuit 94. The output of the data register90 is connected to the data decoder 92 which is coupled to a summingnetwork or junction 96 as is a S-microsecond stimulation trigger outputof the mode logic circuit 94. The mode logic circuit 94 is additionallycoupled to a multiplexer 98 and to a stimulating counter 112 to which itprovides a presetting signal. The output of the stimulating counter 112is connected to a counter full decoder circuit 114 whose output is fedback to the mode logic circuit 94. A digital frequency divider l 16 isconnected to the output of the 100 KHZ oscillator to feed clock signalsof 0.1 Hz and 10 KHz, for example, as required to selected circuits suchas the time duration counter 86 and to the stimulating counter 112,respectively. A power supply 118, operating from a 60 Hz power source,provides all of the operating voltages for the transmitter.

Prior to activating the transmitter, the operating instructions listedin FIGS. 1 and 4 are entered into the transmitter via suitable switchessuch as the rotary thumbwheel and selector switches shown in FIG. 3. Thetransmitter converts this information into a digital sequence of wordsthat are transmitted to the im planted receiver 30 at the appropriatetime. The transmitter 10 is activated by the A-C Power Switch whichsupplies the +5 volts and :15 volts to the appropriate electronics viathe power supply 118. No signals are transmitted from'the transmitter atthis time. When the Stimulate Switch is activated, the 100 KHZ seriesswitch 78 is immediately closed which causes the 100 KI-lzpower signalto be inductively coupled to the resonant circuit 36 in the receiver. No27.12 MHZ signal is transmittedyet because the preset memory pulse ofthe receiver has just been activated by the power supply 38 and it mustbe allowed to decay to insure proper reception. Approximately onemillisecond after activation of the Stimulate Switch, the program logiccircuit 84'enables the data register 90 and the data decoder 92 whichoperate together to read the Data Completion Pulse 1 bit), the PositiveAmplitude (10 bits) and the Negative Amplitude (10 bits) that have beenpreviously entered into the transmitter; connect these data into binarybits where a low state or 0 is 5 microseconds in width and a high stateor 1 in microseconds in width; and encode this information onto a 27.12MHz r-f signal by turning on the 27.12 MHz series switch 72 as required.This 21-bit pulse width modulated Amplitude Data Word is then seriallytransmitted to the receiver 30 only once. 1

The program logic circuit 84 permanently inhibits the data register 90and the data decoder 92 after the 21-bit Amplitude Data Word has beentransmitted and it also enables the mode logic circuit 94. The modelogic circuit 94 momentarily presets the stimulating counter 112 via themultiplexer 98 to a count value specified by the Positive PulseDuration. The 10 KHz clock signal from the digital frequency divider 116now causes the stimulating counter 112 to increase its count until it'is full. This state is sensed by the counter full decoder 114 whichcauses the mode logic circuit 94 to momentarily preset the stimulatingcounter 1 12 via the multiplexer 98 to a count value specified by theNegative Pulse Duration. The foregoing sequence is automaticallyrepeated, with the Interpulse Duration, the Positive Pulse Duration andthe Negative Pulse Duration, etc., being used to preset the stimulatingcounter l 12. Each time the stimulating counter 112 is reset by the modelogic circuit 94, a 5-microsecond pulse is generated by the mode logiccircuit 94 which gates the 27.12 MHz series switch 72 through thesumming junction 96 to generate another bit of the 3-bit StimulatingWord.

The Pulse Mode Selector Switch allows the user to determine which one ofthe five stimulating signals shown in FIGS. b, 0, d,fand h should beused to stimulate the nerve. From the basic Stimulation Word, the usercan select either a bipolar pulse, unipolar positive pulse, or unipolarnegative pulse stimulation via the Pulse Mode Selector Switch, dependingupon the negative and positive amplitudes that have been entered intothe transmitter via the data register 90. The +DC mode modifies theoperation of the mode logic circuit 94 by inhibiting its recyclingoperation after the initial presetting of the stimulating counter l 12;thus only the ON+"b bit of the stimulation word is transmitted as shownin FIG. 5e. The DC mode modifies the mode logic circuit 94 in a similarmanner except that only the ON+b pulse (at zero microamperes positiveamplitude) and the ON" pulse are transmitted before the mode logiccircuit 94 recycling operation is inhibited.

The Time Mode Selector Switch for the Program Logic Circuit 84determines the time duration that the nerve will be stimulated. TheSingle Cycle mode selection will allow the transmitter to transmit onlyone Stimulation Word. Selection of the Program mode will allowstimulation to occur only for the Program Time Duration which haspreviously been entered into the transmitter through the time durationcounter 86. The method of operation is functionally identical to that ofthe stimulating counter 112 and its associated counter full decoder 114,with the 0.1 Hz clock signal used in lieu of the KHz clock signal. TheContinuous mode selection via the Time Mode Selector Switch will allowstimulation to continue uninterrupted until the Stimulate Switch isdeactivated.

Stimulation of the nerve will cease whenever the Stimulate Switch isdeactivated and the Stimulation Word is completed. This function isperformed automatically when the Time Mode Selector Switch is in eitherthe Single Cycle mode or the Continuous mode. Deactivation of theStimulate Switch will shut off the 100 KHz power signal as soon as theStimulation Word has been completed.

Several different types of transmitters may be used with the implantablereceiver 30. Selection will depend upon the particular need. Thelaboratory transmitter shown in FIG. 4 and described hereinabove wouldbe used by professional personnel in hospitals, clinics and doctorsoffices to collect experimental and diagnostic data and to determine thefixed program parameters to be prescribed for the patients personalpre-programmed transmitter. The pre-programmed transmitter is availablein at least two other configurations: the bedside transmitter and theportable transmitter. Both versions are functionally identical to thelaboratory transmitter except that the operating instructions such asstimulating levels, polarities, time durations, etc., discussedhereinabove, will be pre-programmed. The bedside transmitter willordinarily use conventional 115V a-c power for its operation whereas theportable unit will be battery operated.

The receiver 30 provides a basic bipolar constant current waveform tothe nerve from which four other stimulating modes can be externallyselected. Utilizing the circuitry described herein, the time duration ofany polarity pulse can be varied in real-time from microseconds to 10seconds 'in 10 microsecond intervals. The positive and negativeamplitudes of these current pulses can be externally selected from 0microamperes to 4 milliamperes in 10 microamperes intervals. A pulserepetition of 0.03 Hz to 16.7 KHZ can be obtained, for example. Theshape of the current pulses will generally always be rectangular, havinga O to percent rise and fall time of less than 3 microseconds.

As previously expressed hereinabove, five types of stimulating signalsmay be applied to a nerve, for example. Referring again to FIGS. Sa-Sh,the basic bipolar waveform available from the receiver 30 is shown at5b. This corresponds to the basic stimulation word shown at 5a. Bysetting either the negative or positive polarity to 0 microampere, apositive unipolar current pulse 50 or a negative unipolar current pulse5d can be obtained. A programmable steadystate current level of eitherpolarity can also be generated from either unipolar current pulse byextending the time duration of the current pulse as shown at Sfand 5h.The stimulation currents shown at 5f and 5h correspond to the DCstimulation words shown at 5e and 5g, respectively.

The receiver 30 can be divided into two major sections: the power supplycircuit 38 and the signal processor network 50. The function of thepower supply circuit 38 is to generate the required electrical power forthe implanted electronics and to provide two control signals to thesignal processor network 50. The KHz tuned center-tapped coil 32 is usedas the secondary of the power double-tuned coupling circuit 20, 36 todevelop the 100 KHZ power signal. This signal is rectified, filtered,and regulated to provide stable operating voltages for the electronics.The Memory Preset and Safety Release control signals are generated fromthe supply voltages to preset the memory circuit and release the safetyshunt circuit, respectively. These latter circuits will be more fullyexplained hereinafter.

The function of the signal processor network 50 is to receive,demodulate, and process all operational instructions that are sent fromthe transmitter 10 and to generate with the aid of the power supply theproper stimulating amplitude, polarity and time duration signal. The27.12 MHz tuned coil 44 is used as a secondary of the signal doubletunedcoupling circuit 28, 48 to develop the instructions that were sent fromthe transmitter. The first 21 bits of instructions is the Amplitude DataWord which is demodulated and stored in the receiver memory circuit. Allremaining bits are considered as stimulation instructions and aredemodulated and decoded as such. These stimulation instruc-. tionsselect either the Negative Amplitude Word or the Positive Amplitude Wordor neither word from the receiver memory circuit. The selected amplitudeword, if selected, is converted to an analog signal which controls theinverting constant current amplifier. This amplifier then forces theproper constant current signal through the nerve and will be more fullydiscussed hereinafter.

Referring now to FIG. 6, the receiver 30 is shown as comprising thepower supply circuit 38 which includes the 100 KHz tuned circuit 36connected to a full-wave rectifier which provides positive and negativeunregulated voltages to respective voltage regulators 122,

124. The negative unregulated voltage from the fullwave rectifier 120 isalso connected to a safety shunt control circuit 126. In addition tosupplying the positive operating voltage to the signal processor network50, the output of the positive voltage regulator 122 is connected to apreset circuit 128. The output of the negative voltage regulator 124supplies the negative operating voltage to the signal processor network50.

In the signal processor network 50 the 27.12 MHz tuned circuit 48 isconnected to an r-f demodulator 130 whose output is interconnected witha 21-bit shift register (memory) 132 to couple in the overall DataSignal, and to a mode logic circuit 134 and a stimulation decoder 136 toprovide the necessary clock pulses. The mode logic circuit 134 has oneoutput connected to provide a Shift Register Clock to the 2l-bit shiftregister 132 and another output connected to provide a StimulationInhibit Signal to the stimulation decoder 136. Also coupled to the shiftregister 132 is a Memory Preset Signal from the output of the presetcircuit 128 in the power supply 38. The shift register 132 has an outputconnected to provide a Data Completion Pulse to the mode logic circuit134. A IO-line output (for the 10 bits) is connected to provide thePositive Amplitude Word to a positive word multiplexer 138, and another10-line output (for the other 10 bits) is connected to providetheNegative Amplitude Word to a negative word multiplexer 140. An output ofthe stimulation decoder 136 is connected to the negative wordmultiplexer 140 and provides the ON-' Signal. A second similar outputfrom the stimulation decoder 136 provides the ON+ Signal to themultiplexer 138. A third output from the stimulation decoder 136provides an OFF" Signal and it is coupled to an interpulse shunt circuit142 the output of which is connected to receiver output conductors 52,54. A IO-line output of the positive word multiplexer 138 is connectedto a positive digital-to-analog converter 144 whose output in turn iscoupled to an inverting X4 current amplifier 146. A 10- line output ofthe negative word multiplexer 140 is connected to a negativedigital-to-analog converter 148. Theoutputs of both converters 146, 148are coupled to an inverting constant current amplifier 150 whose outputis connected to receiver output conductors 52, 54. Also connected toreceiver output conductors 52, 54 is a safety shunt circuit .152 .whichreceives a safety rel ease signal as appropriate from the safety shuntcontrol circuit. 126 in the power supply 38.

'In operation, the digital instructions from the transmitter 10 arereceived by the 27.12 MHz tuned circuit 48 and fed to the r-fdemodulator 130 which comprises a voltage doubler diode detector and alow pass filter. The pulsed r-f data signal from the transmitter 10comprises the 2 l-bit Amplitude Data Word and a series of StimulationWords. Each Stimulation Word comprises three S-inicroseconds r-f pulses.The r-f demodulator 130 converts the pulsed 27.12 MHz r-f signal to arectified positive video signal which serves as the Clock. The ClockSignal is used in three separate applications: it passes. through thelow pass filter which serves as a pulse width discriminator to derivethe Data Signal for the 21-bit shift register 132, it is used in themode logic circuit 134 to generate the Shift Register Clock for-theshift register 132, and it serves as a trigger signal to the stimulationdecoder 136. Demodulation of the 3-bit Stimulation Word produces threeClock .Signals and no Data Signals because each of the 3-bits is only 5microseconds wide.

The 21-bit register 132, comprising a series grouping of 21 flip-flopcircuits, functions as a memory. It stores a Data Completion Pulse, aPositive Amplitude Word and a Negative Amplitude Word. The memory isinitially cleared by the Memory Preset Signal which is generated by thepreset circuit 128 in the power supply 38. the 2 I -bit Amplitude DataWord is transmitted only after the Memory Preset Signal has beenutilized. The Amplitude Data Word enters into the shift register 132 onthe positive slope of the Shift Register Clock. The Shift Register Clockis an inverted version of the Clock signal which is gated depending uponwhether the receiversystem is in the receive data mode or stimulation"mode. The l-bit Data Completion Pulse enters into the shift register 132first. It is followed by a 10-bit word which represents the negativestimulating current amplitude and another 10-bit word which representsthe positive stimulating current amplitude word. These 21 bits ofinformation are called the Amplitude Data Word, as mentioned previouslyhereinabove. When the Data Completion Pulse has been shifted into theend position of the shift register 132, the Shift Register Clock isinhibited by the mode logic circuit 134 which converts the shiftregister into a static memory.

The mode logic circuit 134 which comprises two NOR gates determines ifan inverted version of the Clock is to go to the shift register 132 asthe Shift Register Clock or if it can be processed by the stimulationdecoder 136. The absence of the Data Completion Pulse indicates that thememory is not full. This forces the Stimulation Inhibit Signal to beactive which inhibits the stimulation decoder 136 while generating andapplying the Shift Register Clock to the memory. The presence of theData Completion Pulse indicates that the memory is full which causes theShift Register Clock and the Stimulation Inhibit Signal to bedeactivated. This essentially converts the shift register 132 to astatic memory and allows the stimulation decoder 136 to be activated.

The stimulation decoder 136 is a divide-by-three" counter with eachstate of the counter indicating the state of the Stimulation Word. Thesethree states are used to generate the time duration and polarity of thestimulating output current to the nerve. The resulting three outputsignals (ON-P, ON-, and OFF") are mutually exclusive in that only onecan be activated by any one time. The presence of the StimulationInhibit Signal disables the counter and forces the OFF to its activationstate. The stimulation decoder 136 is activated only after the 21-bitshift register 132 is full. Only then is it permitted to count thenumber of Clock pulses to determine the state of the 3-bit StimulationWord. The absence of the Stimulation Inhibit Signal then enables thestimulation decoder 136 which activates the ON+ upon receiving the firstclock pulse, the ON" upon receiving the second Clock pulse, and the OFFupon receiving the third Clock pulse. This process is then repeated asoften as required. These outputs alternately select, via the positiveword multiplexer 138 and the negative word multiplexer 140, the PositiveAmplitude Word, the Negative Amplitude Word, or neither of the amplitudewords. The latter condition occurs during the interpulse period andresults in no stimulation of the nerve. Each of the multiplexers 138,140 comprise a grouping of ten AND-OR gates. The polarity and amplitudeof the nerve stimulation signal is achieved by digitally selectingeither the stored Positive Amplitude Word or the stored NegativeAmplitude Word. In each case the amplitude is represented by a -bitword. Two 10-bit multiplex switches, then, are used to select either ofthe two words or neither of them. In no case are both words selectedsimultaneously.

Conversion of the selected lO-bit digitally coded Amplitude Word andconversion of the OFF Word to an analog signal is performed by thedigital-to-analog converters 144, 148. Each of the converters 144, 148comprise a grouping of ten resistors each serially connected to theoutput of a selected AND-OR gate in its appropriate multiplexer circuit138, 140. Each amplitude bit from the multiplexers is weighted by usinga different value for each of the series resistors. The resultingcurrents which flow through the ten resistors .ineach converter 144, 148are summed together to generate a current which is directly proportionalto the digital code. No current results from a digital-to-analogconverter which is fed from an OFF multiplexer. Summation of thepositive amplitude is performed in the inverting X4 current amplifier146 while the negative amplitude is summed in the inverting constantcurrent amplifier 150, each of which comprise an operational amplifiercircuit. [neither case, the summing of the digital-to-analog decodingcurrents is performed by 'an operational amplifier which allows thesummation to occur at zero volts. in this manner, the weighting currentper decoding bit can be accurately established. The weighting currentsfor the Positive Amplitude Word are four times less than that of theNegative Amplitude Word so that less electrical power is consumed by thepositive digital-to-analog converter 144.

The inverting X4 current amplifier 146 performs three functions: it sumstogether the weighting currents of the positive stimulation current; itinverts the polarity of the resulting current so that it will have apositive polarity at the output of the inverting constant currentamplifier 150; and it amplifies the current level by a factor of four tobe compatible with the Negative Amplitude Word. l

The function of the inverting constant current amplifier 150 isthreefold: it provides a constant current source with which the nervewill be stimulated; it sums together the weighting currents of thenegative stimulation current; and it sums in the positive stimulatingcurrent from the inverting X4 current amplifier 146. The latter twofunctions are performed at zero volts to obtain the proper levels. Thesefunctions are performed in the inverting constant current amplifier 150by a unity gain operational amplifier with the nerve being used as thefeedback impedance.

The output current from the inverting constant current amplifier iseffectively shunted out at various times by placing two low impedanceshunt circuits in parallel across the nerve. The safety shunt circuit152 comprises a field-effect transistor having a nominal 60 ohmsimpedance, for example, which is across the nerve at all times exceptwhen the power supply 38 is activated. The state of the safety shuntcircuit 152 is controlled by the safety shunt control circuit 126 whichcomprises a low pass resistor-capacitor filter in which a diode is inparallel with a l megohm resistor to generate the Safety Release Signal.This signal is a modified version of the unregulated negative supplyvoltage from the full wave rectifier 120 and differs from it only inthat an unsymmetrical time delay has been introduced. The time delayoccurs only when the negative voltage is being increased. The absence ofthe negative supply, which may be due to the lack of the 100 KHZcontinuous wave power signal or due to a circuit malfunction, willresult in having the 60-ohm safety shunt circuit 152 across the nerve.Only when the negative supply is present will the low impedance shunt ofthe safety shunt circuit 152 be removed. The other shunt is theinterpulse shunt circuit 142 comprising another field-effect transistorhaving a nominal 75 ohms impedance, for example, which is also acrossthe nerve at all times except when the ON+ and ON states of theStimulation Word are activated. At these times, the interpulse shuntcircuit 142 receives the OFF" Signal from the stimulation decoder 136.When the system is not activated, the two separate shunt circuits areacross the nerve to insure that no extraneous signal pick-up by thesystem will introduce unwanted currents to the nerve. Failure to haveboth power supply voltages present will automatically place one of theshunts across the nerve. This provides a most desirable safety feature.

The 100 KHz continuous wave power signal received by the 100 KHz tunedcircuit 36 is converted into positive and negative d-c voltages. Thesevoltages are filtered and regulated in their respective voltageregulators 122 and 124 to provide stable supply voltages for thereceiver circuits. The function of the preset circuit 128 is to generatethe Memory Preset Signal which is a short duration positive pulse thatpresets the shift register 132 to zero. The Memory Preset Signal isgenerated from the regulated positive supply of the positive voltageregulator 122 when the power supply 38 is first activated. The presetcircuit 128, in its simplest form, comprises a high pass filter thatdifferentiates the regulated positive voltage received from the positiveregulator 122. In another slightly more complex form, the preset circuit128' may be a voltagesensing circuit comprising a serially connectedinput field'effect transistor, zener diode and resistor-togroundcombination connected in parallel across a serially connected resistorand grounded-emitter NPN transistor combination. A capacitor isconnected across the zener diode-resistor series subcombination from'the negative terminal of the zener diode to the ground side of theresistor. The base of the NPN transistor is connected to the positiveterminal of the zener diode; and the collector, connected to thefieldeffect transistor through the series resistor in the NPN circuit,provides the Memory Preset Signal output. The field-effect transistoracts like a constant current diode in this circuit. Besides presettingthe memory of the shift register 132 to zero, this alternative presetcircuit clears the memory and returns the operation back to the enterdata mode from the stimulation mode, if the positive voltage supplydrops below a preset value. Such a situation can arise, for example, bymoving the transmitter probe too far away from the implanted receiverduring operation of the system.

A summary of the operation of the system is as follows:

TIMING SEQUENCE Operation of the system requires four operational timemodes. First the 100 KHZ power is turned on so that the power supply 38can generate the required voltages for the implanted electronics.Second, the desired pulse amplitudes are transmitted via the AmplitudeData Word to the signal processor 50 in digital form where they aredecoded and stored. This phase requires approximately 4,200microseconds. Third, stimulation of the nerve may now begin inreal-time. This phase of the operation will last as long as nervestimulation is required. Fourth, stimulation is terminated by inhibitingthe stimulating word immediately after the OFF bit is transmitted andthen turning off the 100 KHZ power.

The sequence of events which occurs in each of the four time modes islisted below:

Mode l, Turn-On 100 KHz transmitter signal is activated.

. Implantable power supply 38 is activated.

c. Memory cells are preset to via the Memory Preset Signal from thepower supply 38.

. Safety Shunt. 152 is activated to remove its 60 ohm shunt impedancefrom across the output 52, 54.

e. Signal processor 50 is in enter data" status with the stimulationdecoder 136 inhibited.

Mode 2, Transmit Data:

a. 21-bit Amplitude Data Word is serially transmitted.

IAmplitude word is decoded and stored. c. Memory 132 is inhibited as thestimulation decoderl36 is activated.

. Signal processor's 0 is in stimulation mode.

Mode 3, Stimulate a. The first bit of the three-bit Stimulating Wordwill remove the interpulse shunt 142 and will cause the programmedpositive current to flow through the nerve. r

b. The second bit of the Stimulating Word will shutoff the positivecurrent-and will cause the programmed negative current to flow throughthe -nerve.',

c. The thirdfpulse of the Stimulating Word will shutoff the negativecurrent and activate the interpulse shunt 142 across the nerve.

d. Further stimulation of the nerve can be obtained by repeating theabove steps (a through c).

Mode 4, Turn-Off TRANSMISSION AND STORAGE OF THE AMPLITUDE DATA WORD:

' The I desired stimulating amplitudes are transmitted as a coded -bitbinary word along with the l bit Data Complation Pulse. Because of theease of implementing the transmitted logic network 29, a binary codeddecimal format (BCD) is used instead of a coded binary format.

The signal processor 50 receives this word, demodulates it and storesthe coded amplitude bits in its memory. When the Data Completion Pulsehas gone through all of the flip-flops in the shift register 132 and isfinally entered in the last flip-flop, the shift register 132 is lockedby inhibiting its clock and now is employed as a static memory.

During this data transmission mode no stimulation of the nerve isperformed. In fact, the interpulse shunt 142 is deactivated and places anominal ohm impedance across the nerve to prevent voltage buildup on thenerve and to shunt any demodulated signals that might stimulate thenerve.

The presence of the Data Completion Pulse in the last flip-flopsignifies that the Amplitude Data Word has been entered into the shiftregister 132 and that stimulation of the nerve can now be performed inrealtime as commanded by the transmitter 10.

TRANSMISSION AND UTILllZATION OF THE STIMULATION WORD(S):

Stimulating instructions from the transmitter will normally be encodedinto a repetitive 3-bit pulse positioned modulated Stimulation W ord(s).Each Stimulation Word consists of three S-microsecond r-f pulses whichare decoded to derive the time period of each portion of the basicbipolar waveform. The time duration of the Negative Pulse Duration,Positive Pulse Duration, and lnterpulse Duration is determined by thetransmitter from the data entered into it via the thumbwheel switches.The two abbreviated Stimulation Words as described hereinabove areutilized for the and DC Modes.

The stimulation decoder 136 provides three outputs which control thestate of the current pulse to the nerve. These three controls aremutually exclusive in that only one can be on at any one time. The-ON+signal enables only the positive digital-to-analogc'zonverter 144 whichcauses the specified positive stimulating current to flow through thenerve. The ON-' signal enables only the negative digital-to-analogconverter 148 which causes the specified negative stimu'-' latingcurrent to flow. through the nerve. The OFF signal deactivates theinterpulse shunt which places the nominal 75 ohmshunt impedance acrossthe nerve to avoid voltage build-up and to reduce the dc leakage level.

Iclaim:

1. An electronic system for the stimulation of a b. said transmittermeans including transmitter logic network means for receiving andprocessing stimulation and power signal information;

c. said transmitter means additionally including first and second analogchannel network means operably connected to said transmitter logicnetwork means and responsive thereto, said first analog channel networkmeans generating said pulses of radio frequency energy at said firstfrequency containing said digital stimulation signals, said secondanalog channel network means generating said continuous wave energy atsaid second frequency containing said power signals;

. said transmitter means further including first and second resonantcircuit means operably connected to said first and second analog channelnetwork means, respectively, and responsive thereto, said first resonantcircuit means resonant at substantially said first frequency fortransmitting said pulses of radio frequency energy containing saiddigital stimulation signals, and said second resonant means resonant atsubstantially said second frequency for transmitting said continuouswave energy containing said power signals;

e. receiver means adapted to be operably positioned within said livingbody for receiving said pulses of radio frequency energy containing saiddigital stimulation signals at said first frequency and for additionallyreceiving said continuous wave energy containing said power signals atsaid second frequency as transmitted from said transmitter means;

f. said receiver means including third and fourth resonant circuit meansresponsive to said second and first resonant circuit means,respectively, said third resonant circuit means resonant atsubstantially said second frequency for receiving said transmittedcontinuous wave energy containing said power signals, and said fourthresonant circuit means resonant at substantially said first frequencyfor receiving said transmitted pulses of radio frequency energycontaining said digital stimulation signals:

g. said receiver means additionally including power supply circuit meansoperably connected to said third resonant circuit means and responsiveto said continuous wave energy containing said power signals received bysaid third resonant circuit means for providing said operating voltagesfor said receiver means; and

h. said receiver means further including signal processor network meansoperably connected to said power supply circuit means and to said fourthresonant circuit means, said signal processor network means responsiveto said operating voltages from said power supply circuit means andadditionally responsive to said pulses of radio frequency energycontaining said digital stimulation signals at said first frequency forproviding stimulating signals to said biological system.

2. The electronic system defined in claim 1, wherein said first, second,third and fourth resonant circuit means each comprise in combination acapacitor and an associated inductor, said inductors of said first andfourth resonant circuit means each being an antenna operablesubstantially at said first frequency and said inductors of said secondand third resonant circuit means each being an antenna operablesubstantially at said second frequency.

3. The electronic system defined in claim 1, wherein said first analogchannel network means comprises oscillator means for generating saidradio frequency energy at said first frequency, switch means coupled tosaid oscillator means responsive to said transmitter logic network meansfor combining said radio frequency energy at said first frequency withsaid digital stimulation signals, and amplifier means connected to saidswitch means for amplifying signals received through said switch means.

4,v The electronic system defined in claim 1, wherein said second analogchannel network means comprises oscillator means for generating saidcontinuous wave energy at said second frequency, switch means coupled tosaid oscillator means responsive to said transmitter logic network meansfor combining said continuous wave energy at said second frequency withsaid power signals, and amplifier means connected to said switch meansfor amplifying signals received through said switch means. I

5. The electronic system defined in claim 1, wherein said signalprocessor network means includes:

a. a radio frequency demodulator operably connected to said fourthresonant circuit means and responsive thereto;

b. shift register means operably connected to said radio frequencydemodulator for receiving a data signal from said radio frequencydemodulator and for providing a positive amplitude word, a negativeamplitude word and a data completion pulse, said shift register meansalso operably connected to said power supply circuit means for receivinga memory reset signal therefrom.

c. mode logic circuit means operably connected to said radio frequencydemodulator and to said shift register means for receiving a clocksignal from said radio frequency demodulator and for receiving said datacompletion pulse from saidvshift register means, said mode logic circuitmeans providing a shift register clock also said shift re-v gister meansand for providing a stimulation inhibit signal;

said radio frequency demodulator and to said mode logic circuit meansfor receiving a triggering clock signal from said radio frequencydemodulator and for receiving said stimulation inhibit signal from saidmode logic circuit means, said stimulation decoder means s providingmutually exclusive output signals including ON+, ON and' stimulationdecoder means operably connected to shift register means and forreceiving said ON signal from said stimulation decoder means;

negative digital-to-analog converter means operably connected to saidnegative word multiplexer means and responsive thereto for cnvertingsaid negative amplitude word to an analog signal;

positive digital-to-analog converter means operably connected to saidpositive word multiplexer means and responsive thereto for convertingsaid positive amplitude word to an analog signal;

i. inverting X4 current amplifier means operably connected to saidpositive digital-to-analog converter means and responsive thereto forproviding an output signal amplified by substantially a factor of fourto be compatible with said negative amplitude word;

j. inverting constant current amplifier means operably connected to saidinverting X4 current amplifier means and to said negativedigital-toanalog converter means and responsive thereto for providingsaid stimulating signals to said biological system; and

. shunt circuit means operably connected to said stimulation decodermeans and to said power supply circuit means for receiving said OFF"signal from said stimulation decoder means and for receiving a safetyrelease signal from said power supply circuit means to provideprotection against undesired stimulating signals.

6. The electronic system defined in claim 5, wherein said shunt circuitmeans comprises interpulse shunt circuit means operably connected tosaid stimulation decoder means for receiving said OFF". signal andsafety shunt circuit means operably connected to said power'supplycircuit means for receiving said safety release signal, said interpulseshunt circuit means and said safety shunt circuit means operably coupledin parallel across said biological system.

7. The electronic system defined in claim 1, wherein said power supplycircuit means comprises:

a. full-wave rectifier means operably connected to said third resonantcircuit means and responsive thereto for converting said continuous waveenergy received from said third resonant circuit means into positive andnegative d-c voltages;

. positive voltage regulator means operably connected to said full-waverectifier means for receiving said positive d-c voltages from saidfull-wave rectifier means and for providing regulated positive operatingvoltages for said receiver means;

. preset circuit means operably connected to said positive voltageregulator means and responsive e. safety shunt control circuit meansoperably connected to said ne ative voltage re ulator means andresponsive t ereto for provi mg a safety release signal for saidreceiver means.

8. A transmitter for generating; transmitted pulses of radio frequencyenergy at a first frequency containing digital stimulation signals forthe stimulation of a biological system in a living body and foradditionally generating transmitted signals of continuous wave energy ata second frequency containing power signals, said transmittercomprising:

a. logic network for receiving and processing stimulation and powersignal information;

first and second analog channel network means operably connected to saidlogic network means and responsive thereto, said first analog channelnetwork means generating said pulses of radio frequency energy at saidfirst frequency containing said digital stimulation signals, said secondanalog channel network means generating said continuous wave energy atsaid second frequency containing said power signals, said first analogchannel network means including:

1. first oscillator means for generating said radio frequency energy atsaid first frequency,

2. first switch means coupled to said first oscillator means responsiveto said logic network means for combining said radio frequency energy atsaid first frequency with said digital stimulation signals, and

. first amplifier means connected to said first switch means foramplifying signals received through said first switch means,

said second analog channel network means including:

1. second oscillator means for generating said continuous wave energy atsaid second frequency,

2. second switch means coupled to said second oscillator meansresponsive to said logic network means for combining said continuouswave energy at said second frequency with said power signals, and

second amplifier means connected to said second switch means foramplifying signals received through said second switch means; and (firstand second resonant circuit means operably connected to said first andsecond analog channel network means, respectively, and responsivethereto, said first resonant means resonant at substantially said firstfrequency for transmitting said pulses of radio frequency energycontaining said digital stimulation signals, and said second resonantcircuit means resonant at substantially said second frequency fortransmitting said continuous wave energy containing said power signals.

9. The transmitter defined in claim 8, wherein said first and secondresonant circuit means each comprise in combination a capacitor and anassociated inductor, said inductor of said first resonant circuit meansbeing an antenna operable substantially at said first frequens cy andsaid inductor of said second resonant circuit means being an antennaoperable substantially at said second frequency.

1. An electronic system for the stimulation of a biological system in aliving body, said system comprising: a. transmitter means adapted to beoperably associated externally of said living body for generatingtransmitted pulses of radio frequency energy at a first frequency andfor additionally generating transmitted signals of continuous waveenergy at a second frequency, said pulses of radio frequency energyincluding digital stimulation signals for stimulating said biologicalsystem, said continuous wave energy including power signals forproviding operating voltages in said system; b. said transmitter meansincluding transmitter logic network means for receiving and processingstimulation and power signal information; c. said transmitter meansadditionally including first and second analog channel network meansoperably connected to said transmitter logic network means andresponsive thereto, said first analog channel network means generatingsaid pulses of radio frequency energy at said first frequency containingsaid digital stimulation signals, said second analog channel networkmeans generating said continuous wave energy at said second frequencycontaining said power signals; d. said transmitter means furtherincluding first and second resonant circuit means operably connected tosaid first and second analog channel network means, respectively, andresponsive thereto, said first resonant circuit means resonant atsubstantially said first frequency for transmitting said pulses of radiofrequency energy containing said digital stimulation signals, and saidsecond resonant means resonant at substantially said second frequencyfor transmitting said continuous wave energy containing said powersignals; e. receiver means adapted to be operably positioned within saidliving body for receiving said pulses of radio frequency energycontaining said digital stimulation signals at said first frequency andfor additionally receiving said continuous wave energy containing saidpower signals at said second frequency as transmitted from saidtransmitter means; f. said receiver means including third and fourthresonant circuit means responsive to said second and first resonantcircuit means, respectively, said third resonant circuit means resonantat substantially said second frequency for receiving said transmittedcontinuous wave energy containing said power signals, and said fourthresonant circuit means resonant at substantially said first frequencyfor receiving said transmitted pulses of radio frequency energycontaining said digital stimulation signals: g. said receiver meansadditionally including power supply circuit means operably connected tosaid third resonant circuit means and responsive to said continuous waveenergy containing said power signals received by said third resonantcircuit means for providing said operating voltages for said receivermeans; and h. said receiver means further including signal processornetwork means operably connected to said power supply circuit means andto said fourth resonant circuit means, said signal processor networkmeans responsive to said operating voltages from said power supplycircuit means and additionally responsive to said pulses of radiofrequency energy containing said digital stimulation signals at saidfirst frequency for providing stimulating signals to said biologicalsystem.
 2. The electronic system defined in claim 1, wherein said first,second, third and fourth resonant circuit means each comprise incombination a capacitor and an associated inductor, said inductors ofsaid first and fourth resonant circuit means each being an antennaoperable substantially at said first frequency and said inductors ofsaid second and third resonant circuit means each being an antennaoperable substantially at said second frequency.
 2. second switch meanscoupled to said second oscillator means responsive to said logic networkmeans for combining said continuous wave energy at said second frequencywith said power signals, and
 2. first switch means coupled to said firstoscillator means responsive to said logic network means for combiningsaid radio frequency energy at said first frequency with said digitalstimulation signals, and
 3. first amplifier means connected to saidfirst switch means for amplifying signals received through said firstswitch means, said second analog channel network means including: 3.second amplifier means connected to said second switch means foramplifying signals received through said second switch means; and c.first and second resonant circuit means operably connected to said firstand second analog channel network means, respectively, and responsivethereto, said first resonant means resonant at substantially said firstfrequency for transmitting said pulses of radio frequency energycontaining said digital stimulation signals, and said second resonantcircuit means resonant at substantially said second frequency fortransmitting said continuous wave energy containing said power signals.3. The electronic system defined in claim 1, wherein said first analogchannel network means comprises oscillator means for generating saidradio frequency energy at said first frequency, switch means coupled tosaid oscillator means responsive to said transmitter logic network meansfor combining said radio frequency energy at said first frequency withsaid digital stimulation signals, and amplifier means connected to saidswitch means for amplifying signals received through said switch means.4. The electronic system defined in claim 1, wherein said second analogchannel network means comprises oscillator means for generating saidcontinuous wave energy at said second frequency, switch means coupled tosaid oscillator means responsive to said transmitter logic network meansfor combining said continuous wave energy at said second frequency withsaid power signals, and amplifier means connected to said switch meansfor amplifying signals received through said switch means.
 5. Theelectronic system defined in claim 1, wherein said signal processornetwork means includes: a. a radio frequency demodulator operablyconnected to said fourth resonant circuit means and responsive thereto;b. shift register means operably connected to said radio frequencydemodulator for receiving a data signal from said radio frequencydemodulator and for providing a positive amplitude word, a negativeamplitude word and a data completion pulse, said shift register meansalso operably connected to said power supply circuit means for receivinga memory reset signal therefrom. c. mode logic circuit means operablyconnected to said radio frequency demodulator and to said shift registermeans for receiving a clock signal from said radio frequency demodulatorand for receiving said data completion pulse from said shift registermeans, said mode logic circuit means providing a shift register clockalso said shift register means and for providing a stimulation inhibitsignal; d. stimulation decoder means operably connected to said radiofrequency demodulator and to said mode logic circuit means for receivinga triggering clock signal from said radio frequency demodulator and forreceiving said stimulation inhibit signal from said mode logic circuitmeans, said stimulation decoder means providing mutually exclusiveoutput signals including ''''ON+'''', ''''ON-'''' and ''''OFF''''signals; e. positive word multiplexer means operably connected to saidshift register means and to said stimulation decoder means for receivingand selecting said positive amplitude word from said shift registermeans and for receiving said ''''ON+'''' signal from said stimulationdecoder means; f. negative word multiplexer means operably connected tosaid shift register means and to said stimulation decoder means forreceiving and selecting said negative amplitude word from said shiftregister means and for receiving said ''''ON-'''' signal from saidstimulation decoder means; g. negative digital-to-analog converter meansoperably connected to said negative word multiplexer means andresponsive thereto for converting said negatiVe amplitude word to ananalog signal; h. positive digital-to-analog converter means operablyconnected to said positive word multiplexer means and responsive theretofor converting said positive amplitude word to an analog signal; i.inverting X4 current amplifier means operably connected to said positivedigital-to-analog converter means and responsive thereto for providingan output signal amplified by substantially a factor of four to becompatible with said negative amplitude word; j. inverting constantcurrent amplifier means operably connected to said inverting X4 currentamplifier means and to said negative digital-to-analog converter meansand responsive thereto for providing said stimulating signals to saidbiological system; and k. shunt circuit means operably connected to saidstimulation decoder means and to said power supply circuit means forreceiving said ''''OFF'''' signal from said stimulation decoder meansand for receiving a safety release signal from said power supply circuitmeans to provide protection against undesired stimulating signals. 6.The electronic system defined in claim 5, wherein said shunt circuitmeans comprises interpulse shunt circuit means operably connected tosaid stimulation decoder means for receiving said ''''OFF'''' signal andsafety shunt circuit means operably connected to said power supplycircuit means for receiving said safety release signal, said interpulseshunt circuit means and said safety shunt circuit means operably coupledin parallel across said biological system.
 7. The electronic systemdefined in claim 1, wherein said power supply circuit means comprises:a. full-wave rectifier means operably connected to said third resonantcircuit means and responsive thereto for converting said continuous waveenergy received from said third resonant circuit means into positive andnegative d-c voltages; b. positive voltage regulator means operablyconnected to said full-wave rectifier means for receiving said positived-c voltages from said full-wave rectifier means and for providingregulated positive operating voltages for said receiver means; c. presetcircuit means operably connected to said positive voltage regulatormeans and responsive thereto for providing a memory preset signalcomprising a short duration positive pulse for said receiver means; d.negative voltage regulator means operably connected to said full-waverectifier means for receiving said negative d-c voltages from saidfull-wave rectifier means and for providing regulated negative operatingvoltages for said receiver means; and e. safety shunt control circuitmeans operably connected to said negative voltage regulator means andresponsive thereto for providing a safety release signal for saidreceiver means.
 8. A transmitter for generating transmitted pulses ofradio frequency energy at a first frequency containing digitalstimulation signals for the stimulation of a biological system in aliving body and for additionally generating transmitted signals ofcontinuous wave energy at a second frequency containing power signals,said transmitter comprising: a. logic network for receiving andprocessing stimulation and power signal information; b. first and secondanalog channel network means operably connected to said logic networkmeans and responsive thereto, said first analog channel network meansgenerating said pulses of radio frequency energy at said first frequencycontaining said digital stimulation signals, said second analog channelnetwork means generating said continuous wave energy at said secondfrequency containing said power signals, said first analog channelnetwork means including:
 9. The transmitter defined in claim 8, whereinsaid first and second resonant circuit means each comprise incombination a capacitor and an associated inductor, said inductor ofsaid first resonant circuit means being an antenna operablesubstantially at said first frequency and said inductor of said secondresonant circuit means being an antenna operable substantially at saidsecond frequency.